1. Field of the Invention
The present invention relates to a shield wiring technique which increases the difficulty of physically analyzing a semiconductor chip to prevent fraudulent reading and tampering of security information.
2. Background Art
In recent years, circuitry information and internal information of semiconductor devices have required a considerably high level of confidentiality and secrecy. Especially in the field of IC cards, the safety of semiconductor devices is an essential feature and, therefore, it is necessary to protect important information from fraudulent analysis and prevent tampering and copying of internal information. In view of such, there has been a technique for shield wiring in the uppermost wiring layer such that a mask pattern is hidden in order to prevent reading of a mask pattern and circuit analysis with a probe on a wire which may be performed for the purpose of copying and tampering of a semiconductor chip.